In recent years, with the change in food life to European and American styles, large intestine cancer is remarkably increasing in Japan, too and the importance of large intestine examination has been rapidly recognized.
Nowadays, progress and propagation of diagnostic imaging by computed tomography (X-ray CT), ultra-sonography (US), magnetic resonance imaging (MRI), etc. are remarkable, and these diagnostic imagings have been also incorporated into the diagnostic region of tubular organs such as the large intestine. However, most of large intestine diseases stem from lesions occuring in mucosa, and for discovery of such lesions, as a matter of course, but also for grasping of detailed characteristics of the lesions, enema X-ray examination and endoscopy have been utilized as important means.
The enema X-ray examination methods known in the prior art may be broadly classified into the filling method, the double contrast method, the compression method, the mucosal relief method, etc., and according to the present standard of Ministry of Health and Welfare of Japan (reevaluation result), it is approved to use 200 to 2,000 ml of a 20 to 130 w/v % barium sulfate contrast medium.
Among these methods, since double contrast barium enema is optimum for imaging of lesions and diagnosis thereof, it holds the primary place in the current examinations.
The double contrast barium enema is a method, in which barium sulfate, a positive contrast medium, is coated as a thin layer on the inner walls of the large intestine, and air, a negative contrast medium, is simultaneously insufflated to inflate the large intestine, whereafter X-ray transmission is performed to image the state of the large intestine mucosa surface.
The double contrast barium enema includes the Fisher method (1923) in which an aqueous barium sulfate suspension with a concentration of about 40-50 w/v % is injected as a contrast medium after washing the intestine, the contrast medium is discharged out of the body and then air is insufflated before taking double contrast images; the Welin method (1953) in which after washing the intestine with quantities of water or enema as the primary treatment an aqueous barium sulfate suspension with a high concentration of about 100 w/v % is likewise charged into the intestine as a medium, the contrast medium is discharged out of the body and again a small amount of the contrast medium is injected with insufflation of air before taking double contrast images; and the modified Brown method (1963) in which the contents of the large intestine are removed without washing of the intestine by carrying out the preliminary treatment of application of strict diet control combined with administration of laxative, a barium sulfate contrast medium is charged into the intestine and double contrast images are taken without accompaniment of discharging of the barium sulfate contrast medium. Further, the modified Brown method has been improved so as to be well adapted for the Japanese and to give good double contrast images.
This modified Brown method is a method, in which after removal of the large intestine contents by injestion of low fat and low fiber meals (meals for contrast enema) combined with administration of laxative (saline laxative and contact evacuant), 200-300 ml of an aqueous barium sulfate suspension of a relatively higher concentration of about 60-80 w/v % is injected as a contrast medium into the intestine and, without being discharged, permitted to reach the deepest possible point of the large intestine by rolling the patient before insufflation of air for fluoroscopy or photographing. According to this method, it has become possible to visualize the state of the large intestine mucosa as fine network patterns.
Generally speaking, when a barium sulfate contrast medium which has been heretofore used in practice is used to conduct X-ray examination by double contrast method, if the concentration of barium sulfate used is low, the amount of barium sulfate coated is not enough to give good double contrast image, while as the concentration is higher, the amount coated on the intestinal mucosa is increased, but the coating of barium sulfate on the intestinal mucosa surface becomes too thick to give a fine network pattern, and also difficulty is frequently encountered in moving the contrast medium throughout the intestinal tract. For this reason, ordinarily, a barium sulfate contrast medium with a concentration of 60 to 80 w/v % has been used in X-ray examination by double contrast method.
In double contrast barium enema by use of a conventionally used contrast medium containing barium sulfate at a concentration of 60 w/v % or higher, due to X-ray intransmission at contrast medium pools which tend to be formed at flexures of bowels, imaging of intestinal walls is almost impossible, and further when another intestinal tract overlapping the intestine to be imaged in the X-ray direction by fluoroscopy exists, imaging of the overlapping intestinal portion is totally impossible.
For this reason, in order to perform diagnosis without overlookings, it is ideal to carry out examination of the whole large intestine with as small amount of contrast medium as possible (around 150 to 200 ml) so that no pooling may occur. However, since the large intestine extends with a complicated steric structure, a considerable skill is required for the technologist in delivering the injected contrast medium to the depths of the large intestine by way of rolling the patient.
Also for coating the contrast medium well on intestinal walls, it is necessary to conduct the rolling of the patient in different and in detailed manners, which means that the method imposes much burden on physically handicapped patients and aged people.
Further, as for the contrast medium coated on intestinal walls, thin layers thereof are cracked with lapse of time, it thus being necessary to complete photographing relatively quickly and hence a further skill of the technologist being demanded in order for these different requirements to be met.
With respect to the small intestine, such diseases as are peculiar thereto, for example, Crohn disease and malignant tumors, have recently come to be reported and the importance of small intestine examinations has been pointed out.
In the examination of the small intestine, X-ray examination is mainly employed because of the extreme difficulty of performing endoscopic examination in this case. The X-ray examination methods for the small intestine may be broadly classified into the oral administration method, the complete reflux small bowel examination and the peroral intubation method, among which the X-ray examination by double contrast method using the complete reflux small bowel method is considered best for the purposes of the diagnosis of organic lesions in the small intestine.
The peroral intubation method is a method in which a sound is inserted to the depths of the duodenum and a barium sulfate contrast medium and air are infused direct into the small intestine to obtain contrast images. In this method is used a barium sulfate contrast medium comprising a barium sulfate aqueous suspension with a concentration of 50 to 70 w/v %. It is impossible to use such a barium sulfate contrast medium for the purpose of obtaining double contrast images all over the small intestine.
Thus, the small intestine consists of the jejunum and the ileum and its overall length is six to eight times that of the large intestine. Many flextures exist in the small intestine and there is a difference in the mucous membrane structure between the jejunum where villi are well developed and much mucilage is produced and the ileum where villi are not so well developed and mucilage is not produced so much. For these reasons, it is difficult to achieve homogeneous adhesion in the jejunum and the ileum with barium sulfate contrast media conventionally used in practice. Further, since these contrast media are subject to flocculation during passage through the intestinal tract, it is impossible to obtain homogeneous double contrast images all over the small intestine.
Furthermore, because of the peristalsis being strong in the jejunum and weak in the ileum, the movement of barium sulfate contrast medium in the intestinal tract is fast in the upstream portion and gets slower as the medium proceeds to the downstream portion of the small intestine. When the barium sulfate is used at a concentration of 40 w/v % or lower, the transfer in the intestinal tract gets faster but the coating ability is lowered with the result that no satisfactory double contrast images are obtainable. At concentrations higher than 40 w/v %, the flowability is lost to such an extent that the infused barium sulfate contrast medium reaches the ileocecal region with difficulty.
Due to the fact that the small intestine has many flexuous or overlapping portions, barium sulfate contrast medium pools tend to be formed when radiography of the small intestine X-ray examination by double contrast method is conducted by using a barium sulfate concentration of 50 to 70 w/v %, that is in the same manner as described above for the large intestine. No imaging of the intestinal walls at these contrast medium pools is possible because of X-rays being unable to be transmitted therethrough. Moreover, those intestinal portions overlapping these pools in the X-ray direction by fluoroscopy cannot be delineated.
Accordingly, attempts to conduct the small intestine X-ray examination by double contrast method lead to no satisfactory results. This method therefore needs to be supplemented by the compression method which, can be applied, to the jejunum but disadvantageously, not to the ileum because of anatomical differences.